The present invention relates to a device for providing a seal between a shaft and a housing. In particular, the present invention relates to a dynamic seal device for preventing oil from leaking out of a housing and/or for preventing contaminants from traveling into the housing. The present invention also relates to a method of assembling a sealed system.
Prior art devices for sealing a rotating shaft are disclosed in U.S. Pat. No. 4,022,479 (Orlowski) and U.S. Pat. No. 5,024,451 (Borowski). Seal devices of this type may be used to prevent oil from escaping out of a bearing housing and/or to prevent contaminants from working their way into the housing. The prior art devices are formed of at least two ring-shaped members that rotate with respect to each other when the shaft is rotated. One of the members is fixed to the housing and does not rotate. The other member rotates with the rotating shaft.
The two ring members should be located very close together, particularly when the seal device is used to isolate the bearing from small particulate contaminants. Even small quantities of such contaminants are capable of significantly deteriorating the bearing. To prevent such contamination, the two relatively rotatable ring members must be held together very closely, with only a very narrow space therebetween.
The ring members of the Orlowski seal device are connected together by a separate securing means, not shown in the prior art patent. The ring members themselves have no means for establishing and maintaining a narrow spacing therebetween. Therefore, the prior art seal device cannot be manufactured as a unit with a preset, fixed spacing. The spacing between the ring members has to be set when the seal device is installed into the housing. This leaves room for human error outside the control of the device manufacturer. In particular, the Orlowski device can be improperly installed, with the ring members located too far apart to perform satisfactorily. Another problem with the Orlowski device is that the ring members may be separated subsequent to installation, for example by high pressure cleaning spray.
The ring members of the Borowski device are held together by a bead and a groove provided on the ring members themselves. The bead fits within the groove with an interference fit. This arrangement is an improvement over the Orlowski system in the sense that no separate securing means is needed. But the Borowski device is still unsatisfactory because the bead must be resiliently deformed to be positioned within the groove, and the groove must be correspondingly enlarged to receive the deformed bead. The deformation of the bead during assembly makes it difficult to achieve the desired close positioning between the two ring members, as explained in more detail below.
Some prior art references refer to the use of a rotor and a stator, the latter including a plurality of alternating annular grooves and ridges and an axial groove. The grooves and ridges catch oil thrown by the rotating shaft. The oil then drains by gravity to the axial groove which allows the oil to travel back into the housing.
These types of sealed systems may have deficiencies in applications where the shaft rotates at low revolutions per minute or the oil has a high viscosity. In either of these applications, the oil may continue to travel along the shaft beyond the alternating grooves and ridges.